The present invention relates to an ink jet recording method, apparatus and recording head using thermal energy.
In conventional ink jet recording machines, various controls are effected for the purpose of stabilizing the ink ejecting direction (accuracy in the record spot) and stabilizing the ejection amount (Vd (Pl/dot)) in order to minimize the image density variation or non-uniformity in the recorded image or the like.
The controls include controlling the ink temperature (temperature control) and controlling ink viscosity which is influential to the ink ejection amount. In the type of the recording apparatus in which a bubble is formed in the ink by thermal energy, and the ink is ejected by the expansion of the bubble, the bubble creating conditions or the like are controlled to stabilize the ejection amount. As for the specific structures for the ink temperature control, the use is made with a heater (exclusively for this purpose or an ejection heater commonly used for this purpose) for heating the recording head containing the ink and a temperature sensor for detecting the temperature relating to the recording head. The temperature detected by the temperature sensor is fed back to the heater. As an alternative, the temperature feedback is not effected, and the recording head is simply heated by the heater.
The heater and the temperature sensors may be mounted on a member constituting the recording head or on an outside portion of the recording head.
For another method for the control of the ejection amount or the like or a method usable with the above-described method, there is a method in which a pulse width of a single pulse (heat pulse) applied for the purpose of production of the thermal energy to an electrothermal transducer (ejection heater) for producing the thermal energy in the above-described type of ejection, so that the quantity of the generated heat is controlled to stabilize the amount or quantity of ejection.
The types of the control are classified in the following four groups:
(1) The head temperature control is carried out at all times (outside/neighborhood) with the temperature feedback;
(2) The head temperature control is carried out if necessary (outside/neighborhood) with the temperature feedback;
(3) The high temperature head control (higher than the ambient temperature) is carried out with the temperature feedback; and
(4) Pulse width modulation of a single heat pulse.
In group 1, since the recording head temperature is always controlled, the evaporation of the water content of the ink due to the heating is promoted. Therefore, increase or solidification of the ink in the ejection outlet of the recording head may be brought about with the possible result of deviation of the ejection direction or the ejection failure. In addition, the density change or non-uniformity may result due to the relatively high dye content in the ink. They ultimately degrade the image quality. Another influence by the continuous heating by the heater is the change in the head structure and the deterioration of the material constituting the recording head with the result of decrease in the reliability and durability of the recording head. Generally speaking, this control is easily influenced by the change in the ambient temperature and the self temperature rise due to the printing operation. More particularly, the ejection amount varies with the result of density variation or non-uniformity.
In group 2 system, the temperature control operation is carried out if necessary, and therefore, it is an improvement of group 1 type. However, since the temperature control is carried out after the printing instruction is produced, the predetermined temperature is required to be reached in a relatively short period, and therefore, large energy (heat generating quantity (W) of the heater) is required for the heating. This results in increase of the temperature ripple increase in the temperature control with the result of impossibility of correct temperature control. If this occurs, the ejection quantity may change due to the temperature ripple with the result of image density variation or non-uniformity. If an attempt is made to correctly effect the temperature control, it is required that the energy supply is reduced. If this is done, the time required for reaching the target temperature becomes longer, and the waiting period for the start of the printing increases.
In group 3 system, the target temperature is made higher than the ambient temperature so as to avoid the influence of the temperature change due to the ambient temperature change or the self temperature increase due to the printing operation. By this, it is possible to reduce the variation in the ejection quantity of the ink during the printing of low duty. However, in the high duty printing operation, for example in a solid black printing, the influence of the temperature rise cannot be avoided since the temperature rise due to the printing is high.
As for a temperature control, the temperature outside the recording head may be controlled. This is advantageous in that the influence of the ambient temperature can be reduced. However, the response to the self temperature rise is not satisfactory, and therefore, it is easily influenced by the self temperature rise.
If the temperature control in the neighborhood of the recording head is carried out, for example, by mounting the heater or the temperature sensor on an aluminum plate functioning as a base plate for supporting the heater board having the ejection heater, then, the response is improved and is effective against the temperature rise due to the printing. However, since the thermal capacity of the base aluminum plate is large, the temperature ripple results. Because of the temperature ripple, the ejection quantity may vary.
In group 4 system, a pulse width is modulated using a single pulse. However, it is considered that a further improvement is required in order to increase the reproducibility to permit correct ejection amount control from the standpoint of increasing the high image quality, because the controllable range of the ejection amount capable of accommodating the ejection amount variation resulting from the temperature change in the bubble forming ink jet system, and because it is difficult to provide the linearity in the ejection amount with the increase of the pulse width therein.
In addition to the problem of the ejection amount variation, the problem resulting from the self-temperature rise of the recording head is that ejection property variation during the printing due to the ink temperature variation is brought about and that the controlling property variation is brought about because of the variation in the head structure. These may lead to the variation in the ejecting direction, ejection failure and the refilling frequency reduction. If these occurs, the image quality can be extremely degraded.
Since the ink head cartridge is mass-produced, some variations are unavoidable in the area of the heater board, the resistance, the film structure, the sizes of the ejection outlets or the like formed in a silicone chip through a semiconductor manufacturing process. Therefore, the variations possibly exist in the ink ejection quantities for the ink individual outlets in one recording head and in the performance of the individual recording head.
The variation in the ejection property of the recording head may result in the variation in control properties during the printing as well as the initial ejection quantity of the ink. Among various recording head ejection properties, what is particularly significant in the image formation are variation in the ink ejection quantity of the individual recording heads and the variation in the control property.
Another problem is that a non-uniform temperature distribution is produced depending on the number of nozzles used, with the result of non-uniformity or the like.
More particularly, it is not the fact that the printing operation is effected using all of the nozzles. For example, it is probable that the printing operation is carried out using only one half of the nozzles. In other words, the printing region is not an integer multiple of a printing width of the recording head, and therefore, on the bottom line of the printing, only a part of the nozzles is used for the printing.
When the ink jet recording apparatus is operated in response to a control signal supplied from external equipment such as a reading apparatus, the number of nozzles of a recording head is required to be changed from the normal printing operation. For example, in the serial printing type ink jet recording apparatus, it is so designed that the sheet feeding accuracy is stabilized in the normal feeding (head width), and therefore, if the sheet feeding speed is changed for a reduced printing, the accuracy is influenced with the result of connecting stripe (disturbance to the image). In view of this, two-pass-printing in which two printing operations are is effected for one feeding of the sheet, is effective. In such a case, it is required that the printing operation is carried out with changed number of ejecting nozzles.
If the number of printing nozzles of a recording head is changed, a non-uniform temperature distribution is produced depending on which ejection heaters are actuated. This non-uniform temperature distribution results in variation in the ejection amount. In an ink jet recording apparatus in which the head drive is controlled by the temperature sensor, the print density becomes non-uniform unless the control is made in consideration of the temperature distribution.
In the recent ink jet recording apparatus, the clearance between the recording head and the recording material is changed depending on the material of the recording material (plain paper, coated sheet, OHP sheet or the like) or the recording system (one path or two paths). This may result in the deterioration of the ink deposition position accuracy.
This problem is directly influential to the image quality of the print. Particularly, in the case of a full-color print produced by four ink materials, i.e., cyan, magenta, yellow and black ink materials, for example, the ejection property variation results in the ejection amount variation if ejection property different from the normal properties appear in one recording head. As a result, the color balance is disturbed, so that the coloring and the color reproducing property is deteriorated (increase in the color difference). In the case of a monochromatic recording in a black color, a red color, a blue color or a green color, a density variation such as a production of a stripe due to the ink ejection failure in a solid image, becomes remarkable. In addition, the fine line reproducibility and the character quality are degraded due to the deviation in the ejecting direction.
As an advantage of an ink jet recording apparatus, the recording is possible on a wide range of recording mediums. Examples of relatively frequently used mediums include usual recording sheet of paper, thick paper such as envelope, an overhead projector (OHP) transparent sheet or the like. Among these recording material or mediums, the OHP sheet is required to have a high density printing so that the printed character and the images are clear when it is projected through an overhead projector.
Therefore, it is desirable to control the variation in the ejection amount, and that the printing is effected with a desired high image density particularly on the OHP sheet.
Accordingly, it is a principal object of the present invention to provide an ink jet recording method and apparatus wherein the amount or quantity of the ink ejection is stabilized irrespective of the temperature change attributable to the ambient temperature change and the self temperature rise (due to the printing operation).
It is another object of the present invention to provide an ink jet recording method and apparatus capable of reducing the influence of the self temperature rise.
It is a further object of the present invention to provide an ink jet recording apparatus using a recording head detachably mountable thereto in which the variation in the initial ink ejection quantity resulting from the manufacturing steps for the recording head can be corrected to provide proper ejection quantity.
It is a further object of the present invention to make it possible to make ejection heads because of too much or less ejection quantities usable, thus increasing the yield of the recording heads, so that the head manufacturing cost is reduced.
It is a yet further object of the present invention to provide an ink jet recording method and apparatus in which the variation in the ink ejection quantity attributable to the non-uniform temperature distribution depending on the individual ejection outlets, can be reduced.
It is a further object of the present invention to provide an ink jet recording method and apparatus wherein even if the temperature of the recording head varies due to the ambient temperature and the self temperature rise, the ink ejection speed and the ink refilling frequency can be properly controlled.
It is a further object of the present invention to provide an ink jet recording method and apparatus wherein when the recording is effected on an OHP sheet, the recording density can be increased to provide proper ejection quantity.
It is a further object of the present invention to provide an ink jet recording method and apparatus wherein the quantity of the ejected ink can be stably changed in a wide range.
According to an aspect of the present invention, there is provided a recording method in which ink is ejected by thermal energy produced by a heat generating element of a recording head in response to application of a driving signal thereto, comprising the steps of: changing a waveform of the driving signal in accordance with a temperature of the recording head; and selecting a fixed waveform of the drive signal when the temperature of the recording head exceeds a predetermined level.
According to another aspect of the present invention, there is provided an ink jet recording apparatus in which ink is ejected, comprising: a recording head having a heat generating element to eject the ink by thermal energy produced by the heat generating element in response to a drive signal thereto; temperature detecting means for detecting a temperature of the recording head; drive signal changing means for changing a waveform of the driving signal in accordance with an output of said detecting means; and control means for disabling said changing means and providing a predetermined waveform of the driving signal when the output of said detecting means is indicative of a predetermined temperature or higher.
According to a further aspect of the present invention, there is provided a thermally operable recording head detachably mountable on a main assembly of a recording apparatus, comprising: means for receiving actuating signal including a first drive signal having different width from the recording apparatus; and information storing means for storing information for changing the width of the first drive signal when the information is supplied to the main assembly.
According to a further aspect of the present invention, there is provided a recording apparatus, comprising: a recording head driven by an actuating signal including a first drive signal having a variable width; and drive signal changing means for reading information for determining the width from information storing means of said recording head and changing the width of the first drive signal to be supplied to said recording head.
According to a further aspect of the present invention, there is provided an ink jet recording apparatus in which ink is ejected, comprising: ink ejection outlets; ejection heaters corresponding to said ink ejection outlets; temperature sensor means; an ink jet recording head having said ink ejection outlets, said ejection heaters and said temperature sensor means; driving means for driving said recording head with different driving conditions in accordance with an output of said temperature sensor means; and changing means for changing the driving conditions in accordance with ejection outlets used for recording operation.
According to a further aspect of the present invention, there is provided an ink jet recording apparatus in which ink is ejected, comprising: a plurality of ink ejection outlets; ejection heaters corresponding to said ink ejection outlets; plural temperature control heaters; plural temperature sensors; an ink jet recording head including said ejection outlets, ejection heaters, temperature control heaters and said temperature sensors; driving means for driving said recording head with different driving conditions in accordance with outputs of said temperature sensors; and changing means for changing the driving conditions in accordance with said ejection outlets used for recording operation.
According to a further aspect of the present invention, there is provided an ink jet recording apparatus in which ink is ejected, comprising: an ink jet recording head for producing a bubble in the ink by thermal energy generated by heat generating elements responsive to a driving signal to eject the ink by expansion of the bubble; and control means for controlling a speed of the expansion of the bubble, wherein the driving signal includes a first pulse having a pulse width P1, an interval having a width P2 and a second pulse having a width P3 in the order named in which P1xe2x89xa6P2 less than P3, and wherein the expansion speed is controlled by changing a waveform of the first pulse.
According to a further aspect of the present invention, there is provided an ink jet recording apparatus in which ink is ejected, comprising: a recording head having an energy generating element for producing energy contributable to eject the ink; recording head driving means for applying driving signals to said energy generating elements; temperature detecting means for detecting temperature relating to said recording head; changing means for changing a waveform of the drive signals in accordance with an output of said detecting means; and drive control means for fixing the waveform to a predetermined waveform when a recording material used is an OHP sheet.
According to a further aspect of the present invention, there is provided an ink jet recording apparatus using a recording head provided with electrothermal transducers, which is operable in different recording modes for different recording materials, comprising: recording means operable in a first recording mode for a first recording material having transparent portion and a second recording mode for usual recording material; changing means for changing drive signals supplied to the electrothermal transducers in accordance with a result of temperature detection relating to the recording head; wherein changeable ranges of the driving signals are different for the first recording mode and for the first recording mode, wherein the range for the first recording mode includes a maximum driving signal in the range for the second recording mode.
According to a further aspect of the present invention, there is provided an ink jet recording apparatus, comprising in which a bubble is created in ink by thermal energy generated in response to a drive signal applied to a heater, and the ink is ejected onto a recording material by expansion of the bubble, comprising: driving means for applying plural driving signals to said heater per one ink droplet ejection, wherein the plural driving signals include a first driving signal for increasing a temperature of the ink adjacent the heater without creating the bubble and a second drive signal after the first drive signal with an interval therebetween, for ejecting the ink, wherein the thermal energy by the first drive signal is transferred to the ink adjacent the heater during the interval; changing means for changing an amount of the ejected ink by changing a width of the first drive signal, wherein the interval is not shorter than the width of the first drive signal even when the width of the first drive signal is about its maximum.
According to a further aspect of the present invention, there is provided an ink jet recording method in which a bubble is created in ink by thermal energy generated in response to a drive signal supplied to a heater, and the ink is ejected onto a recording material by expansion of the bubble, and in which plural driving signals are supplied to the heater per one droplet ejection of the ink, comprising the steps of: supplying a first drive signal effective to increase a temperature of the ink adjacent the heater; providing a rest period after application of the first drive signal, wherein the rest period is long enough to permit the thermal energy produced by the heater in response to the first drive signal to transfer to the ink adjacent the heater; supplying a second drive signal effective to create a bubble in the ink to eject the ink; and changing a width of the first drive signal to adjust an amount of ejected ink, wherein the rest period is not shorter than the width of the first drive signal even when the width of the first drive signal is about its maximum.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.